Angular measurements can be made by noting the directions of objects relative to a reference direction. It is with respect to the accuracy of the angular measurement wherein the various prior art apparatus differ. Theoretically, the accuracy .phi. of angular sighting of objects is determined by the Rayleigh or diffraction limit of a lens, namely .phi.=.lambda./D, where .lambda. is the wavelength and D is the size of aperture. This means that the angular measurement cannot be made better than the limit prescribed by diffraction. Thus, once the wavelength .lambda. and aperture size D have been selected, the theoretical accuracy of the angular measurement is known. In practical terms however, the theoretical accuracy of a lens is seldom achieved especially as the wavelength .lambda. decreases toward and beyond optical wavelengths. This is due to the fact that small detectors become increasingly size limited at the shorter wavelengths so that putting a detector behind a lens will capture more area than the image area produced by the lens. However, this problem is yielding to recent advances in the art of large scale integration (LSI) which allows the high density packaging of detectors onto a small surface which can then be used to sample the focal plane of a lens. Notable among such recent detectors for its small size and unloading ease is the optoelectric charge coupled image sensor. This sensor has already been put to use in a wide range of imaging applications.
Charge transfer image sensors have been developed using a variety of technologies including solid state (SS), charge coupled devices (CCD), charge injection devices (CID), and bucket brigade devices (BBD). These devices are used to view an object scene or picture and to convert light intensity from the object scene into electrical signals. Transmitted to a remote location, these signals can reproduce an image of the real object scene with high resolution. Linear image sensors consist of a single row of photoelements and, therefore, image a single line of optical information. If a frame, i.e., a number of lines, of optical information is desired either the image or the device must be moved from line to line to obtain the information. Linear image sensors are used in facsimile, slow scan TV, optical character recognition or label reading systems. They also find application in monitoring industrial processors where the processed items are inspected as they pass the linear sensor. Area image sensors, on the other hand, find applications in the imaging of two dimensional object scenes, usually under low light level illuminations and providing compact, light-weight low power-consuming and stable operating long-life camera systems. Area imagers consist of a rectangular array of photoelements. Like the linear devices there are different methods of reading out the stored video information obtained by the photoelements. For example, the information in the photoelements can be read out serially, in serial-parallel, and in parallel formats. Image sensors, their architectures and methods of operation have been described in a number of publications including the article by Amelio "Charge Coupled Devices" appearing in the May, 1974 issue of Scientific American, in the article by Solomon "CCD Image Sensors" appearing in Paper 2 presented at the IEEE Western Electronic Show and Convention (WESCON) Los Angeles, Sept. 10-13, 1974, in the article "A new imaging technology grabs hold: Charge Transfer Devices" appearing in the Mar. 15, 1974 issue of Electronic Design, and in the article by Deliduka "Enormous Bucket-Brigade Optical Scanner Achieves High Efficiency" appearing in the February, 1976 issue of Computer Design. Commercially available image sensors and associated equipment are shown in the brochure of Reticon Corp., entitled Product Summary Solid State Image Sensors and Systems, published in 1973.
Present image sensors work splendidly when the object or view scene is stationary relative to the sensor and even work in a limited respect as the object scene moves across the sensor's field of view at relatively low speed. However, the capability of present image sensors quickly degrades at speeds beginning to approach the modest value of a small fraction of one kilometer per hour. Thus, while the known apparatus and methods of the present image sensors have the ability to form images at stationary and very low speeds they fail at high image speeds. Moreover, there are no known image sensors for measuring angles and speeds much less than for doing so using noncoherent as well as coherent radiations, or for using clock means for signal processing including tracking, or for changing the range focusing of the object scene, or for operating at high rates of motion of the object scene, or for operating at other than optical frequencies.
Present image sensors require that the angular motion of the object be low enough so that the signal being detected does not exceed the response time of the detector. Obviously, there is a trade between a small detector to obtain high angular accuracy and a large detector to obtain useful response when the object moves. This problem is well known in the prior art. Thus, while small size detector arrays are not available these have not been applied to either the angular measurement or the object motion problems, their use being confined to the imaging of stationary or slowly moving objects without angular measurement or motion compensation and to imaging of objects using time delay integration (TDI). Thus, while the known apparatus of the prior art image sensors have the ability to form images at stationary and low object speeds or for using TDI techniques to from images at faster object speeds, they totally fail to provide angular measurements of objects and motion compensation other than TDI. Moreover, there are no known image sensors for measuring angles using noncoherent as well as coherent radiations, or for using clock signals for motion compensation, or for operating at high rates of object motion, or for operating at other than optical frequencies.
Therefore it is an object of the invention to provide apparatus and method for measuring the angles of objects relative to the centerline of a lens or aperture. Another object of the invention is to provide apparatus and method for a goniometer for measuring the bearing of objects. A further object of the invention is to provide apparatus and method for high speed angle measurement in a search, track, or trackwhile-scan detection system.
It is an object of the invention to provide apparatus and method for a velocity meter for measuring the vector speed of objects.
It is another object of the invention to provide apparatus and method for operating using coherent or noncoherent radiation from objects. A further object of the invention is to provide apparatus and method for operating using a stable local oscillator. Another object of the invention is to provide apparatus and method for operating using a synchronous or asynchronous clock.
It is an object of the invention to provide apparatus and method for operating using a clock having error signal inputs for adjusting clock signals. Another object of the invention is to provide apparatus and method for operating using clock signals for object tracking and for motion compensation. A further object of the invention is to provide apparatus and method for operating using a data processor for detecting and correlating pulses from image scanners.
It is another object of the invention to provide apparatus and method for operating using a data processor for generating error signals used for tracking objects and for motion compensation. Another object of the invention is to provide apparatus and method for recording and reproducing holograms. Another object of the invention is to provide apparatus and method for operating using an output display. Yet another object of the invention is to provide apparatus and method for operating at acoustical, microwave, infra-red, and optical wavelengths.